1. Field of invention
This invention relates to a beta voltaic power source integrated with a substrate as a power source for integrated circuits formed on the substrate.
2. Description of related art
Radio isotopic power sources convert radiation from radioactive isotopes directly into electrical energy. Devices, such as artificial cardiac pacemakers, utilize the radio isotopic power sources for sustained long term power which allow the devices to function for many years without any other source of energy.
Tritium is an isotope of hydrogen having a half life of 12.5 years. Because tritium emits only beta particles and the intensity of the beta particles is limited, tritium is an excellent source of radiation for radio isotopic power source applications.
Beta voltaic power sources incorporate tritium together with a pn junction to directly convert the emitted beta particles into electrical energy. The beta particles emitted by the tritium is absorbed by the pn junction generating electron-hole pairs. The electron-hole pairs are separated by the built in electric field of the pn junction producing an electric current. Relatively high efficiencies are possible because each high energy beta particle produces many electron-hole pairs.
Current applications of the beta voltaic power source are in the form of a battery component. The battery is connected to a separate device such as the artificial cardiac pacemaker.